vestigial

Of or pertaining to a vestige or remnant; like a trace from the past.

Not fully developed in mature animals.

Of a vestigial structure; that has lost all or most of its original function in the course of evolution.

Remnants of the vascular supply of lost organs may be present in the tissues of the receptacle when all external evidence of the organs has disappeared. Only rarely does the vascular supply of a vestigial organ disappear while external remnants are still present.

A small, degenerate, or imperfectly developed part or organ which has been more fully developed in some past generation.